Characterization Of Juvenile Fish Habitats Within Estuarine And Coastal Seascapes In Virginia

Identification and protection of high-quality juvenile fish habitats, or nursery habitats, is an integral component of fisheries management. The mid-Atlantic region is experiencing disproportionately greater rates of warming and sea level rise relative to other coastal regions in the United States. These changes may alter or degrade nursery habitats for many recreationally and commercially sought-after fish species in the mid-Atlantic region. Habitat protection and conservation is necessary to safeguard nursery function and sustain recruitment of juvenile fishes to adult populations. To identify habitats for protection, quantification of fish responses to habitat features is needed at multiple spatial, temporal, and ecological scales. The primary goal of this dissertation was to quantify habitat characteristics in Virginia estuarine and coastal ecosystems and relate these characteristics to patterns in species assemblage composition, use and quality of nursery habitats, and habitat associations of juvenile fishes. Each chapter presents and discusses a research question related to juvenile fish habitats, and all chapters explore fish-habitat relationships that have implications for regional habitat conservation and fisheries management. Chapter 1 quantifies estuarine and coastal seascape characteristics at multiple spatial scales and assesses the effects of these characteristics on species assemblages and juvenile fish abundance. The results of this research highlight the importance of considering the broader environmental context of physical habitat structures when assessing the functionality and conservation potential of nearshore areas. Consideration of the entire, heterogenous seascape mosaic as opposed to a single habitat type is warranted when planning aquatic habitat conservation and restoration. Chapter 2 evaluates habitat quality and nursery area function of Virginia estuarine and coastal ecosystems for two economically valuable species, Summer Flounder Paralichthys dentatus and Spot Leiostomus xanthurus, based on juvenile fish abundance, body condition, and growth. Findings from this chapter suggest that tidal marshes are essential juvenile habitat for these species, implying that marsh loss may negatively impact juvenile fish production. Finally, Chapter 3 presents novel information on spatial-temporal habitat use of an ecologically important and imperiled species, Blueback Herring Alosa aestivalis, in Chesapeake Bay subestuaries. Juvenile Blueback Herring use subestuaries for a prolonged period of time during their outmigration from freshwater nurseries to the coastal ocean, and are therefore vulnerable to human disturbances and habitat alterations in subestuaries during this time. This work provides a scientific basis for the Virginia Marine Resources Commission to specify time-of-year restrictions to protect juveniles from mortality induced by in-water construction activities during outmigration. Furthermore, the fish-habitat associations described by this chapter will guide conservation and recovery strategies for this species. Collectively, the research within this dissertation demonstrates that the complexities surrounding fish-habitat relationships demand consideration of habitat and fish responses to habitat at multiple spatial and temporal scales.